Telephone-exchange system.



C. L. GOODRUM.

TELEPHONE EXCHANGE SYSTEM. APPLICATION FILED DEC. 30. 1916.

1,251,505., Patented Jan. 1, 1918.

' ln van/0r:

UNITED STATES PATENT OFFICE.

CHARLES L. GOODBUM, OF NEW YORK, N. Y., ASSIGNOR T0 WESTERN ELECTRIC COM- PANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

Specification of Letters Patent.

Patented Jan. 1, 1918.

Application filed December 30, 1916. Serial No. 139,803.

To all whom it may concern:

Be it known that I, CHARLES L. GooDRUM, a citizen of the United States, residing at New York, in the county of New York and State of New York, have invented certain new and useful Improvements in Telephone Exchange Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to machine switching telephone exchange systems.

Its object is to provide a circuit arrangement wherein, when connection is made to a busy line, the calling party is given a sig nal to indicate the busy condition of such line, this signal also indicating that if he will wait until the line becomes free, his line will be the next to be connected thereto, and if now another party seeks connection with such busy line, he will receive a signal different from the first, indicating to him that the line desired is not only busy, but that a party is waiting for a connection with such line.

In accordance with this invention, a relay is included in the connector test circuit, and operates if the selected line is merely busy, to connect a tone of one character to the calling partys line, but if the line is busy and also has an awaiting call, the relay does not operate, and thereby causes the connection to the calling line of a tone of another character.

More specifically, a pair of relays is provided for each connector, included in series in the test circuit when the'connector is set on the called line. If the line is busy, one of-these relays fails to operate in parallel with the circuit connected to the test multiple at the connector making the tested line busy, and at its back contact provides a holding circuit for the side-switch escape magnet to prevent it from releasing the side switch to the ringing position. The other relay, however, is arranged to operate under the assumed condition, and in attracting its armatures, applies a waiting tone to the calling line and prevents the connector from releasing.

In case the line selected is not only busy, but has a call waiting as just indicated, the other relay also fails to operate, and at an armature and back contact closes the connector release circuit, which applies a busy tone to the calling line.

Referring to the drawings which show only so much of a telephone exchange system as is necessary for a comprehension of the invention, the invention will be readily understood from a description of the operation of the system.

Upon the removal of the receiver by the calling party at substation S, the calling line is automatically connected in any wellknown manner to an idle first selector, the brushes 1, 2, 3 and terminals 4;, 5, 6 only whereof are shown. The calling party then, by means of the sender E, sets the selector in operative relation to the desired group of terminals 4, 5 and 6, whereupon the switch automatically picks out an idle one of these sets of terminals. The calling line is thus extended to a second selector, the brushes 7, 8 and 9 and terminals 10, 11, 12 only whereof are shown, which is likewise set under the control of the sender, in operative relation to the desired group of trunks 10, 11, 12, terminating in connectors having access to the desired substation F. The selector then automatically picks out one of these idle trunks in the well-known manner.

The calling line is thus extended to the connector, and the stepping relay 13 thereof is energized, and energizes a slow relay 14 which, in attracting its left armature, interposes a break in the circuit of connector release magnet 15, and in attracting its right armature, connects the back contact of the stepping relay 13 to the primary stepping magnet 16 of the connector.

The calling party now operates his sender S to transmit impulses corresponding to the tens digit of the wanted number. For each retraction of the armature of stepping relay 13, as the sender operates, an impulse 1S transmitted to magnet 16 over the following circuit, to step the connector brushes 17, 18, 19 in operative relation to the group of terminals containing those of the wanted line 20, 21, 22: free pole of battery, magnet 16, side-switch arm 23, conductor 24, rlght armature and front contact of relay 14, armature and back contact of relay 13 to ground. Upon the first retraction of the armature of stepping relay 13, a slow relay 25 is energized, and remains energized during the transmission of the impulses. This relay, in attracting its inner right armature, energizes the side-switch escape magnet 26. When the sender restores and maintains relay 13 energized, relay 25 after a slight 1n terval becomes deenergized, opening the circuit of the escape magnet 26, which thereupon releases the side switch into position 2. .Arm 23 of the side switch, in this position, substitutes the secondary stepping magnet 27 for the primary magnet 16 in the stepping circuit.

The calling party now operates the sender to transmit impulses corresponding to the units digit of the wanted number. As before, the slow relay energizes upon the first retraction of the armature of relay 13, and remains energized while the impulses are being transmitted to magnet 27, and, in attracting its inner right armature, again energizes the escape magnet 26. lVhen the sender reaches its normal position and maintains the relay 13 energized, relay 25, after an interval, releases its armatures, opening the circuit of escape magnet 26, which releases the side switch into position 3, provided the line is idle. Assuming therefore that the line is idle, the following circuit is closed for relay 25: free pole of battery, relay 25, conductors 37, 38, arm 23 and its third contact, conductors 39, 36, armature and front contact of relay 13 to ground. Relay 25, in attracting its inner right armature, again energizes the escape magnet 26, which, in attracting its armature, closes the ringing circuit as follows: free pole of ringing generator 29, or battery 30, depending upon the position of commutator 31, brush 55, ringing cut-off relay 32, armature and front contact of magnet 26, conductor 33, arm 34 and its third contact, brush 18, conductor-21, the bell at substation F, terminal 20, brush 17, arm 35, conductor 36, armature and front contact of relay 13 to ground. As the side-switch arm 39 reaches its third contact, ground is applied to the test multiples 22 of the selected line over resistance C, to cause the selected line to test busy to ther connectors and to operate the cut-off relay -11 of such line. When the called party removes his receiver, ringing cut-0E relay 32 is energized and opens the circuit of escape magnet 26, which thereupon passes the side switch to position at, in which the ringing current is disconnected from the called line, and the same is connected through to the supervisory relay 10 over the windings of which talking current is fed to the called substation. In position 4 side-switch arm 39 maintains ground connected to test multiples 22 over the resistance C.

Assuming now that the line selected is busy when connection is made thereto. In this event, when the test brush 19 of the testing connector engages the test multiple 22, the following circuit is closed: free pole of battery, cutoft relay 41, test multiple 22, brush 19, arm 39 and its second contact, conductor 42, left armature and back contact of relay 25, relays A and B to ground.

The resistances of relays A and B and resistance C are so arranged that under these conditions the relay B will energize, but the relay A will remain inert. No inter ference with the connection in which substation F is included occurs, because, although by the retraction of the inner right armature of relay 25 upon the continued energization of relay 13, when the sender restores, after having transmitted the units impulses, the original circuit of the escape magnet 26 is opened, the side switch is prevented from passing to the ringing position, due to the closure of a substitute circuit for the escape magnet 26 previously closed which circuit is as follows: free pole of battery, magnet 26, conductors 43, 4:4, secondary olfnormal contact SON, closed on the first secondary step of the connector, conductor 46, right armature and back contact of relay A to ground. Relay B, in attracting its right armature, connects a source of busy tone current 47 over the left armature and back contact of relay A to the lower talking conductor 48, and thus to the calling line. The character of this tone is such as to in dicate to the calling party that the line is busy, but that if he will wait until the substation F becomes idle, without opening the line circuit by depressing his switchhook, his line will be the next to be connected thereto. WVhen the connection in which substation F is involved is disestablished, the side-switch arm 39, in moving back to its normal position. disconnects resistance C from the multiples 22. The removal of this path in multiple with relays A and 13 causes relay A to become energized, due to the resultant increase in the current flow. This relay, in attracting its leftarmature, disconnects the source -17 from the calling line, thus indicating to the party that the desired line has become free, and the attraction of the right armature opens the circuit of the escape magnet 26, which, in de'energizing, passes the side switch to the ringing position. In moving into position 3 arm 39 connects resistance C to the test multiples 22 of line F, thus causing the same to test busy to other connectors and the bell at substation F is rung as hereinbefore described, from which point on the operations are the same as those traced.

Assuming now that when the connection is attempted two connectors are already set upon multiples of substation F. In that event the side switch of one of such connectors is in position 3 or 4 and the side switch of the other is in position 2. When the test brush 19 of the testing connector reaches the multiple 22 and the slow relay 25 retracts its armatures, the following circuit is closed for the release 15 of this connector: free pole of battery, right winding Of magnet 15, right armature and back contact of relay 40, primary off-normal contact PON, resistance I), outer right armature of the waiting connector will maintain its armatures attracted, however. The release magnet, in energizing, restores the con nector to its normal position and locks itself over the following circuit: ground, left winding of magnet 15, conductor 60, left armature and front contact of relay 14, conductor 61, terminal 12, brush 9, magnets 62,

63 of the preceding selectors in parallel, free pole of battery. The arms 67, 66 of the side switches of these selectors at this time are in their third positions. Magnets 62, 63 are marginal. and do not energize due to the hlgh resistance of the left winding of mag net 15. At 1ts rlght armatureand front contact the release magnet connects a sourceof busy tone current 50 to the lower talking conductor 48. The character of this busy tone is such as to indicate to the calling party that not only is the desired line busy, but that a party is awaiting connection thereto. IVhen, however, the calling party replaces his receiver this winding is shunted out and the magnets 62 and 63 become energized and release the corresponding selectors. The denergization of the connector release magnet disconnects busy tone source 50 from the lower talking conductor.

After the parties to a connection are through talking and replace their receivers, the circuit to release the connector is as follows: free pole of battery, right winding of magnet 15, right armature and back contact of relay 40, contact PON, left armature and back contact of relay 14L, conductors 61 and 51, left armature and back contact of relay 40, right armature and back contacts of relays 14: and 13 to ground.

It will be noted that during the secondary movement of the connector the relays A and B are disconnected from the test brush 19 at the left armature and back contact of relay 25 which is energized during the transmission of the units impulses, and also that this relay, at its outer right armature and back contact, maintains the release magnet 15 disconnected from the armature and back contact of relay B at this time to prevent premature release.

The resistance D is provided for the purpose of making the release magnet 15 slow to attract its armatures, in order to pre vent a momentary engagement between the outer right armature of relay 25 and its back contact from releasing the connector.

This momentary contact occurs when the slew relay 25 retracts its armatures, upon the termination of the transmission of the units set of impulses, to open the circuit of escape magnet 26 to pass the side switch to position 3. Inposition 3, however, the circuit traced for relay 25 is again immediately closed and this relay attracts its armature before magnet 15 can become sufficiently energized to withdraw the holding pawls. WVhat is claimed is:

1. In a telephone exchange system, the V combination with telephone lines, automatic I switches, senders associated with said lines forsetting said switches to interconnect said lines, means for causing the selected line to test busy, means actuated when a switch is set on a busy line togive a signal -of one character to the calling party and to maintain said switch on said line, means actuated when another switch is set on said busy line to give a signal of another character to the calling party initiating the last connection, and means actuated when said busy line becomes idle for signaling the same and for connecting the line first connected thereto.

2. In a telephone exchange system, the combination with telephone lines, automatic switches, senders associated with said lines for setting said switches to interconnect said lines, a source of signaling current, means for automatically connecting the same to the called line if idle, means for causing the selected line to test busy, means actuated when connection is made to a busy line for maintaining the connection thereto and for preventing the connection of said source to said line and for giving a busy signal of one character to the calling party, means actuated when a second connection is made to said busy line to give a signal of another character to the calling party initiating such second connection, and means actuated when said busy line becomes idle for automatically connecting said source to said line and for connecting the first calling line thereto.

3. In a telephone exchange system, the combination with telephone lines, automatic switches, senders associated with said lines for setting said switches to interconnect said lines, a source of signaling current, means for automatically connecting the same to the called line if idle, means for causing the selected. line to test busy, means actuated when connection is made to a busy line for maintaining the connection thereto, for preventing the connection of said source thereto and for giving a busy signal of one charac-' ter to the calling party, means actuated when a second connection is made to said busy line to release such connection and to give a signal of anothercharacter tothe calling party initiating such second connection, and means actuated when said busy line becomes idle for automatically connecting said source to said line and for connecting the first calling line thereto.

4. In a telephone exchange system, the combination with telephone lines, means for interconnecting said lines including a connector, senders associated with said lines for setting said connectors on said lines, a relay for said connector, sources of busy current of different character, a test circuit including said relay and the test terminal of the called line operative to cause said relay to energize and connect one of said sources to the calling line if only one switch is connected to the selected line, said circuit being inoperative to energize .aid relay and thereby to cause the other of said sources to be connected to the calling line if more than one switch is connected.

5. In a tele )hone exchan e s stem the sistance C, means for connecting said re sistance to the test multiples of the selected line when connection is made thereto to cause the same to test busy, a pair of relays A, B, a circuit including said relays and the test multiple of a busy line in parallel with the circuit includingresistance C, the circuit conditions being such that relay B is energized to connect said source of waiting busy tone to the calling line and relay A remaining inert to provide a substitute circuit for the escape magnet to prevent the 7 side switch from passing from the ringing position, the restoration of the connector first set on said line disconnecting resistance 0 from the test terminal, whereupon relay A is energized to open said substitute circuit, whereupon the side switch passes to the ringing position.

In witness whereof, I hereunto subscribe my name this 29th day of December A. D.,

CHARLES L. GOODRUM.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. G." 

